The invention is directed to a printed circuit board connector element with a plurality of signal contacts arranged grid-like in columns and rows in a spring clip of insulator, and with a shielding unit that contains a first and second ground lamina that are conductive, are arranged at opposite sides of at least one of the signal contacts and that are conductively connected to one another via a bridge, whereby the shielding unit comprises a first ground terminal projecting from it that can be conductively connected to the printed circuit board.
Such a printed circuit board connector element is disclosed by German reference DE 44 10 047 A1.
Low-frequency printed circuit board plug connectors are being increasingly operated with faster digital signals. The extremely steep leading signal edges correspond to high frequencies. Problems with the signal transmission quality thereby arise; in particular, undesired cross-talk effects arise between neighboring signal contacts. On the other hand, it is foreseeable that both assemblies with very fast signals as well as assemblies with signals that are less fast will be employed in future devices. This gives rise to the need to connect and operate both frequency-optimized spring clips as well as standard spring clips by plugging to standard blade connector on the device backplane.
The problem of cross-talk can be conventionally solved in that the signals are conducted over only every second contact, whereas the intervening contacts are occupied with ground. In this solution, however, the plurality of terminals usable for the signal transmission is drastically reduced, so that it seems poorly suited for applications with a high signal density.
German reference DE 40 40 551 C2 discloses that a cross-talk between terminals neighboring one another in neighboring, vertical rows be prevented by inserting a shielding element between the vertical terminal rows of a spring clip. What is disadvantageous about this solution, however, that only three of the five available contact rows are usable for signals and two rows are occupied with ground.
A shielding unit with two bulkhead sheets connected by a bridge is in fact known from the initially cited Published Application. However, only connector elements--see FIGS. 2, 7 and 8--wherein a first, front half of the signal contacts of a column is directly shielded by the shielding unit belonging to this column are proposed therein. The other half of the column is shielded by two further shielding elements that are arranged at the columns adjacent at the left and right and respectively extend thereat only along the second, back half of the signal contacts. This known design solution has the disadvantage that respectively one signal contact in every column must be occupied with ground since a shielding unit is provided for each column, which is already involved in terms of fabrication technology. What is also disadvantageous in view of manufacture is the fact that two different shielding elements are employed as well as the complicated assembly sequence that derives overall. As viewed in terms of the functioning of the shielding, the known solution is problematical insofar as each shielding unit therein is connectable to the printed circuit board with only one terminal to ground, as a result whereof the reflux current cannot follow the ideal path.